Interband spectrum of weakly coupled stochastic lattice Ginzburg-Landau models

We analyze the excitation spectrum of the generator associated with the relaxation rate to equilibrium in weakly coupled stochastic Ginzburg-Landau models on a spatial lattice Z(d). The spectrum has a quasiparticle interpretation. Depending on d and on the specific interaction, by solving the Bethe-Salpeter equation in the ladder approximation, we show the existence of a stable particle above the upper envelope of the two-particle band, possessing a concave dispersion curve. This result furthers our knowledge about the spectrum of the stochastic dynamics generator.